| 摘要 |
PURPOSE:To widen the control band for radial feed and also to reduce the track pitch by obtaining a phase difference between a signal outputted in a cycle corresponding to the shift speed of a recording optical system in the radius direction of a master disk revolving at a fixed speed and a signal outputted in a cycle corresponding to the set speed and controlling the shift speed of said optical system in order to eliminate said phase difference. CONSTITUTION:The revolving speed of a glass master disk 3 is set at a fixed level, and the shift speed of a recording optical part 11 is decided by the size of the disk 3 and a track pitch to be produced. A control part 6 delivers a drive signal to a feed motor 15 and starts the radial feed of the part 11 so as to obtain said shift speed. At the same time, the part 61 supplies the result of measurement of the shift distance of the part 11 through a laser length measurement device 9 and performs a phase comparison between a reference pulse train corresponding to the shift speed decided previously and the shift frequency of the part 11 based on a pulse train, i.e., the result of measurement. Thus a phase deviation is calculated. Then the part 61 controls the motor 15 so as to set the phase difference at zero and performs the speed control so that the radial feed speed of the part 11 is always coincident with a fixed speed decided previously. |
